Just in time for Halloween, I Know What You Did Last Summer turned 20.

Directed by Jim Gillespie, the classic slasher movie was a big break for many stars. For instance, Johnny Galecki, who played Max Neurick in the film, went on to star as Leonard Hofstadter in the hit series The Big Bang Theory, and Sarah Michelle Gellar, who played Helen Shivers, went on to play Buffy Summers in the popular TV series Buffy the Vampire Slayer. It was also a big film for stars Ryan Phillippe, Jennifer Love Hewitt and Freddie Prinze Jr..

Besides launching some of these stars' careers, the movie sparked a bit of romance. Prinze, who played Ray Bronson, ended up marrying Gellar in 2002. Although the two didn't play a couple in the movie, they went on a dinner date a few years after the movie debuted. The couple has been married for 15 years and has two kids. They also starred in the 2002 Scooby-Doo movie together as Fred and Daphne.

"We were just friends. That's one of the reasons I think our relationship has always been so good," Prinze previously told E! News. "We were just friends for a good two years before we ever went on a date. She knew what kind of guy I was. She knew what my morals were, what my priorities were and vice versa. We already kind of knew all the faults in the other person."

He added, "We ended up being the perfect balance. But it didn't happen until years after and there was a solid foundation built, and that's probably the main reason why we've always been cool and groovy."

To see pictures of the I Know What You Did Last Summer stars then and now, check out the gallery.

Columbia Pictures / Warner Bros.

Johnny Galecki as Max Neurick

Now that he no longer plays Max Neurick, he plays Leonard Hofstadter on the Big Bang Theory.

Columbia Pictures / CBS

Muse Watson as Ben Willis

After playing Ben Willis, Watson went on to star in Prison Break and NCIS.

Columbia Pictures / NBC

Anne Heche as Missy Egan

Since playing the role of Missy Egan, the actress appeared in Everwood, Ally McBeal and Adventure Time. She also starred in Six Days Seven Nights with Harrison Ford.

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Columbia Pictures / Access Motion Pictures

Bridgette Wilson as Elsa Shivers

After playing Elsa Shivers, Wilson appeared in the rom-com The Wedding Planner. She was also on the show The $treet.

Columbia Pictures / Getty Images

Freddie Prinze Jr. as Ray Bronson

The Ray Bronson character married his co-star Sarah Michelle Gellar. He also starred in the hit She's All That,Freddie and Scooby-Doo.

Columbia Pictures / USA Network

Ryan Phillippe as Barry Cox

Phillippe married Reese Witherspoon; however, the couple later divorced. The actor later appeared in Cruel Intentions andTheLincoln Lawyer.

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Columbia Pictures / Getty Images for GILT

Sarah Michelle Gellar as Helen Shivers

This Emmy-winning actress married her co-star Freddie Prinze Jr. They have two kids. She also starred as Buffy Summers in Buffy the Vampire Slayer.

Columbia Pictures / CBS

Jennifer Love Hewitt as Julie James

After starring as Julie James, Hewitt went on to act in several major television shows, including Ghost Whisperer, The Client List and Criminal Minds.

For those of you who haven't seen the movie, I Know What You Did Last Summer is about four teenagers who get in an accident and try to hide the victim's body by throwing it into the sea. However, their act comes back to haunt them one year later when one of the characters receives a note saying "I know what you did last summer." It soon becomes clear that someone is out for revenge.

The 1997 movie was such a hit that it led to two sequels I Still Know What You Did Last Summer and I'll Always Know What You Did Last Summer.